1. Dismiss Notice
  2. This forum is for support and discussion only. Please promote test prep materials/services (including AMAs) in the Special Offers subforum only. Thanks!
    Dismiss Notice
  3. Guest, be sure to check out How To Get Into Dental School, our free downloadable PDF with step-by-step details for dental school applicants!
    Dismiss Notice

Destroyer Question: Ortho > Para?

Discussion in 'DAT Discussions' started by busupshot83, Apr 20, 2007.

  1. busupshot83

    busupshot83 S.D.N. Vet
    7+ Year Member

    Joined:
    Mar 22, 2003
    Messages:
    2,247
    Likes Received:
    3
    Problem #15 in the Destroyer's orgo section has a Cl being added to a benzene with an activating substituent (NH). I understand activating groups direct to the ortho and para positions, but why does it say the ortho is MINOR while the para is MAJOR?
     
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  2. poc91nc

    poc91nc Membership Revoked
    Removed 7+ Year Member

    Joined:
    Nov 5, 2006
    Messages:
    552
    Likes Received:
    0
    Status:
    Dental Student
    Could be because of steric factors...the Loudon book talks about this in ch16.
    Hmmm...the steric interaction could come from the chlorine lone pairs and oxygen on the carbonyl group. Since we are dealing with an amide, the nitrogen is predominantly sp2 and the lone pair is involved in a double bond...if you draw the corresponding resonance structure...the oxygen bears a negative charge (amides are not very reactive relative to other carboxy acid derivatives like esters and acyl chlorides since amides are resonance stabilized). So...unfavorable repulsions between the oxygen and chlorine at the ortho position might play a role in para dominance....that is the only way I can rationalize it.

    Lots of other reactions give para dominance...like nitration of bromobenzene...acylation of toluene...etc
     
  3. jdmsamurai

    2+ Year Member

    Joined:
    Feb 11, 2007
    Messages:
    237
    Likes Received:
    1
    Status:
    Dental Student
    um NH is not an amide its an amine...no carbonyl but overall amide is activating
     
  4. poc91nc

    poc91nc Membership Revoked
    Removed 7+ Year Member

    Joined:
    Nov 5, 2006
    Messages:
    552
    Likes Received:
    0
    Status:
    Dental Student
    Ph-NHCOPh is an amide....not aniline...look at the problem.

    Aniline is more electron donating than the amide...the amide nitrogen is not as free to donate the lone pair
     
  5. poc91nc

    poc91nc Membership Revoked
    Removed 7+ Year Member

    Joined:
    Nov 5, 2006
    Messages:
    552
    Likes Received:
    0
    Status:
    Dental Student
    Yes...amides are activating due to electron donating...but not as good as aniline...big difference.
     
  6. busupshot83

    busupshot83 S.D.N. Vet
    7+ Year Member

    Joined:
    Mar 22, 2003
    Messages:
    2,247
    Likes Received:
    3
    Thanks guys.
     
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  7. 92CamaroLS1

    10+ Year Member

    Joined:
    Dec 7, 2005
    Messages:
    562
    Likes Received:
    1
    Status:
    Dentist
    Ya I think its mostly steric hinderence at the ortho position. You will get both since both have the sigma framework stabilizing effect of added resonance forms, but para is less hindered so I think generally you are going to get more para.
     
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...

Share This Page